To establish whether allergic asthma could be induced experimentally in a nonhuman primate using a common human allergen, three female rhesus monkeys (Macaca mulatta) were sensitized with house dust mite (Dermatophagoides farinae) allergen (HDMA) by subcutaneous injection, followed by four intranasal sensitizations, and exposure to allergen aerosol 3 hours per day, 3 days per week for up to 13 weeks. Before aerosol challenge, all three monkeys skin-tested positive for HDMA. During aerosol challenge with HDMA, sensitized monkeys exhibited cough and rapid shallow breathing and increased airway resistance, which was reversed by albuterol aerosol treatment. Compared to nonsensitized monkeys, there was a fourfold reduction in the dose of histamine aerosol necessary to produce a 150% increase in airway resistance in sensitized monkeys. After aerosol challenge, serum levels of histamine were elevated in sensitized monkeys. Sensitized monkeys exhibited increased levels of HDMA-specific IgE in serum, numbers of eosinophils and exfoliated cells within lavage, and elevated CD25 expression on circulating CD4(+) lymphocytes. Intrapulmonary bronchi of sensitized monkeys had focal mucus cell hyperplasia, interstitial infiltrates of eosinophils, and thickening of the basement membrane zone. We conclude that a model of allergic asthma can be induced in rhesus monkeys using a protocol consisting of subcutaneous injection, intranasal instillation, and aerosol challenge with HDMA.

Clara cells, progenitors for bronchiolar epithelium, are also primary targets for metabolically activated pulmonary cytotoxicants and have an abundance of the cytochrome P-450 monooxygenases required for xenobiotic metabolism. To define the repair pattern after massive Clara cell injury, mice were treated with naphthalene, and lungs evaluated 1-14 days postinjury (DPI). Clara cells of terminal bronchioles were vacuolated and swollen 1 DPI, exfoliated 2 DPI, and resembled controls at 14 DPI. The volume fraction of vacuolated cells was highest 1 and 2 DPI and minimal at 5-7 DPI. The volume fraction of normal nonciliated cells decreased 40% at 1 DPI. Cell proliferation increased within epithelium and interstitium at 1 DPI, was maximal at 2 DPI, and at all other time points was similar to baseline levels. Expression of Clara cell differentiation markers was barely detectable in terminal bronchiolar epithelium at 1 and 2 DPI, clearly detectable at 4 DPI, and gradually returned to control levels at 5-14 DPI. We conclude that bronchiolar epithelial repair after naphthalene injury involves distinct phases of proliferation and differentiation, proliferation of cells that are not differentiated Clara cells, and interaction of multiple cell types including nontarget cells.

No abstract

Deficiency of the frataxin mRNA alters the transcriptome, triggering neuro- and cardiodegeneration in Friedreich's ataxia. We microarrayed murine frataxin-deficient heart tissue, liver tissue and cardiocytes and observed a transcript down-regulation to up-regulation ratio of nearly 2:1 with a mitochondrial localization of transcriptional changes. Combining all mouse and human microarray data for frataxin-deficient cells and tissues, the most consistently decreased transcripts were mitochondrial coproporphyrinogen oxidase (CPOX) of the heme pathway and mature T-cell proliferation 1, a homolog of yeast COX23, which is thought to function as a mitochondrial metallochaperone. Quantitative RT-PCR studies confirmed the significant down-regulation of Isu1, CPOX and ferrochelatase at 10 weeks in mouse hearts. We observed that mutant cells were resistant to aminolevulinate-dependent toxicity, as expected if the heme pathway was inhibited. Consistent with this, we observed increased cellular protoporphyrin IX levels, reduced mitochondrial heme a and heme c levels and reduced activity of cytochrome oxidase, suggesting a defect between protoporphyrin IX and heme a. Fe-chelatase activities were similar in mutants and controls, whereas Zn-chelatase activities were slightly elevated in mutants, supporting the idea of an altered metal-specificity of ferrochelatase. These results suggest that frataxin deficiency causes defects late in the heme pathway. As ataxic symptoms occur in other diseases of heme deficiency, the heme defect we observe in frataxin-deficient cells could be primary to the pathophysiological process.

The lung, which is in intimate contact with the external environment, is exposed to a number of toxicants both by virtue of its large surface area and because it receives 100% of the cardiac output. Lung diseases are a major disease entity in the U.S. population ranking third in terms of morbidity and mortality. Despite the importance of these diseases, key issues remain to be resolved regarding the interactions of chemicals with lung tissue and the factors that are critical determinants of chemical-induced lung injury. The importance of cytochrome P450 monooxygenase dependent metabolism in chemical-induced lung injury in animal models was established over 25 years ago with the furan, 4-ipomeanol. Since then, the significance of biotransformation and the reasons for the high degree of pulmonary selectivity for a myriad of different chemicals has been well documented, mainly in rodent models. However, with many of these chemicals there are substantial differences in the susceptibility of rats vs. mice. Even within the same species, varied levels of the respiratory tract respond differently. Thus, key pieces of data are still missing when evaluating the applicability of data generated in rodents to primates, and as a result of this, there are substantial uncertainties within the regulatory community with regards to assessing the risks to humans for exposure to some of these chemicals. For example, all of the available data suggest that the levels of cytochrome P450 monooxygenases in rodent lungs are 10-100 times greater than those measured in the lungs of nonhuman primates or in man. At first glance, this suggests that a significant margin of safety exists when evaluating the applicability of rodent studies in the human, but the issues are more complex. The intent of this review is to outline some of the work conducted on the site and species selective toxicity and metabolism of the volatile lung toxic aromatic hydrocarbon, naphthalene. We argue that a complete understanding of the cellular and biochemical mechanisms by which this and other lung toxic compounds generate their effects in rodent models with subsequent measurement of these cellular and biochemical events in primate and human tissues in vitro will provide a far better basis for judging whether the results of studies done in rodent models are applicable to humans.